Electronic tube and control therefor



Feb. 3, 1948.

P. H. CRAIG ELECTRONIC TUBE AND CONTROL THEREFOR Filed May 20, 1942 UsHl U5 Paz/mer Cra/y Patented Feb. 3, 948

UNITED STATES PATENT OFFICE ELECTRONIC TUBE AND CONTROL THEREFOR PalmerH. Craig, Gainesville, Fla., assignor to Invex Corporation, New York, N.Y., a corporation of New York Application May 20, 1942, Serial No.443,717

3 Claims. (Cl. 315-268) This invention relates to electronic tubes ofthe space-discharge rectiiier class.

The tube of this invention comprises in general an evacuated envelopecontaining an anode and a cathode and ionizable gas at predeterminedpressure; and provided with a control electrode. The control electrodeis in the form of a loop or band encircling or embracing the dischargepath through the tube between the anode and cathode; and in thepreferred form is a loop or band on the outside of the envelope, but insome cases it may be disposed within the envelope.

The invention resides in an improved method and means for controllingthe discharge current between the anode and cathode by the controlelectrode.

It is among the objects of the invention:

To provide generally an improved electronic tube of the gaseousdischarge rectier class;

To provide an electronic tube of the class referred to having animproved mode of operation;

To provide in connection with an electronic tube of the class referredto, improved means for controlling the discharge current therethrough;

To provide an improved method of controlling the discharge currentthrough an electronic tube of the class referred to.

Other objects will be apparent to those skilled in the art to which myinvention appertains.

My invention is fully disclosed in the following description taken inconnection with the accompanying drawing in which,

Fig. 1 is a side elevational view with parts broken away of a tubeembodying my invention;

Fig. 2 is a diagrammatic view of an electric circuit suitable foroperation and control of the tube of Fig. 1;

Fig. 3 is a cross sectional view taken from the plane 3-3 of Fig. 1,through the envelope wall and a control electrode of the tube, and withthe thickness of the wall and electrode magnied for illustrativepurposes.

Fig. 4 is a diagrammatic view illustrating changes of main tube currentwhich occur upon changing the degree of negative energization of thecontrol electrode of the tube in the practice of the invention.

While my invention is applicable to the type of electronicspace-discharge tube having a cathode in the form of a pool of mercuryor the like, as well as to the type having a heated thermionic emissioncathode, I have chosen to illustrate and describe it herein as appliedto the latter type, since the construction and mode of operation of theparts of the tube embodying my invention are otherwise the same in bothtypes of tubes.

Referring therefore to the drawing, I have shown at I a glass tubeenvelope having on the lower end thereof a metal plug base 2 of theprong type provided with three individual prongs 3, t, and 5, and havingabove the base a pinch 6 in which are sealed terminal conductors con.-nected to the prongs in the usual manner, the terminal conductors beingindicated at 1, 8 and 9. The envelope has been evacuated and containsionizable gas such as argon therein at a predetermined pressure to bereferred to.

In the upper end portion of the envelope I is an anode Il) electricallyconnected to an external terminal II in the usual manner. The anode maybe of graphite, or of molybdenum, or of carbonized nickel, or may be ofother materials such as have been used for the anodes of tubes of thistype. At I2 is shown generally a cathode of the indirectly heated type,and it may be of any suitable construction. One construction which Ihave found suitable is that constituting the subject matter of thecopending application of Palmer H. Craig and John J. Glauber, Serial No.338,194, filed May 31, 1940, for Improvements in discharge rectiiiertubes with indirectly heated cathodes, which issued July 14, 1942, asUnited States Patent No. 2,289,346.

The conductors 1, B and 9 are connected through the pinch 6 to theprongs 3, 4 and 5 respectively. As indicated in Fig. 2, in connectionwith Fig. 1, the main circuit through the tube is from the anode Il),through the gas as a discharge arc to the cathode I2 and thence byconductor 9 to the prong 5; and the circuit for heating the cathode isfrom one prong say the prong 4, by Way of the conductor 8 to the heaterI3 of the cathode (Fig. 2) and back by conductor 'l to the prong 3.

The envelope may be evacuatedas referred to by well-known processes,including heating of the internal structural parts and flashing of agetter or the like, and then gas such as argon is introduced at thedesired pressure.

The general operation of the tube as described is that well-known oftubes of this class. Thermionic coatings on the cathode l2 are heatedand emit electrons and these electrons ionize the gas within theenvelope causing it to emit other electrons, and when potential isimpressed upon the anode and cathode and the anode is positive withrespect to the cathode, a ow of electrons and current occurs from thecathode to the anode in the nature of a discharge.

The control electrode is shown at i4 and is in the form of an externalband outside of and embracing or encircling the envelope I, and it maybe variously constructed. It may be in the form of a separate detachablewire or band of metal; or a band of metal mesh; but preferably 1 providea band which in effect is fused or sealed into the material of the outerwall of the envelope. The preferred process for applying such a bandelectrode is that used in ornamenting glassware with metallic bands orthe like, for example with platinum bands. A so-called "liquid platinumpaint like commercial material is painted in the form of the desiredband on the outer surface of the envelope. The glass and the band arethen heated, and the band takes on the appearance of metal platinum andhas the characteristic of being fused into the glass surface. A bandthus made is electrically conductive, and metal parts can be solderedthereto in strong rigid juncture therewith; and accordingly a Ametal`terminal I5 is soldered to the band ld formed as at it for makingelectrical connection therewith.

lThe electrode Il as shown in Fig. 1 is disposed between the cathode andanode which is its lpreferred position.

When a tube constructed as above described is put into operation and thedischarge flows from the cathode tothe anode under Athe impulsion of the-potential th'ereacross, the maximum amount of current flow, oramperage, is of course determined by the Vline potential from which the.cathode-anode potential is derived and by the resistance of theexternal load circuit; but the actual amperage owing is under thecontrol of the energization of the electrode i4.

Hereinafter when the anode is referred to as of positive sign, it iswith the meaning that it is positive with respect to the cathode, andwhen the control electrode is referred to as negative it is with themeaning that it is negative with respect to the cathode when the anodeis positive with respect to the cathode.

Perhapsthe most useful application of the tube is in the lcontrol ofalternating current load circuits, -and this will be described asillustrative of its uses, although those skilled in the art willunderstand how it may be applied to uses with direct current.

`When the potential impressed upon the anode and cathode is alternating,the ow of current -occurs only during those half waves in which theanode is positive as is well-known, and even Without yenergization ofthecontrol electrode the current is automatically interrupted in each halfcycle in which the anode is negative; and therefore with alternatingcurrent the tube admits of control of the duration ofthe current or thenumber of half cycles thereof after it starts by suitably energizing thecontrol electrode, inasmuch as this electrode can at any time beenergized suiciently to cut ol the flow of current by preventing thecurrent from starting on the next succeeding positive half cycle; and byestablishing a phase relationship between the control electrodevenergizing potential and the anode `to .cathode impressed potential,and controlling the degree .of energization of the control electrode atthat phase relationship, the control electrode cancontrol the effectiveamperage owing at any timef'by changing the time of starting in eachpositive half cycle, to thereby reduce the effective value to a minimumvalue, and vice versa raise it to a maximum.

I have discovered furthermore that lf the control electrode be energizednegatively to a suitable super-negative degree, that is a degree beyondthe degree at which it prevents current flow as described, it will causecurrent again to flow; or if the minimum value of current be flowing itwill Vmaintain it flowing or increase it; and that if thissuper-negative degree of energization be ,further increased, theamperage will be increased Vdirectly or commensurably with the increaseof the super-,negative energization, and vice versa, decreased directlycommensurably when the supernegative energization is decreased.

The control of Athe current through the tube bynegative electrodeenergization may therefore be effected by two methods, as follows:

First, vthere is Va high value of negative energization of the controlelectrode at which the current flow is cut off or reduced to a minimum,as the case may be; and at negative energization below this high value,current dov/'s or increases from the minimum as `the case may be, thecurrent being maxim-um for zero or low electrode energica-tion; and theamperage of the current fiow is inversely commensurable with the degreeof negative energization, being greater for lesser degrees and viceversa.

Second, at suitable super-negative-energization beyond the vsaid highvalue, cu-rrent flows or increases from the minimum as the Vcase may be;

and the amperage of the current flow is directly commensurable with thedegree of super-negative energizatiom being greater for Agreaterdegreees -of super-negative energization and vice versa.

So far as I am aware no gaseous discharge tube has been proposedheretofore the current flow through which lvaries directly commensurablywith the degree of negative energization of a control electrode asdescribed above in the second method of operation. f

I have discovered furthermore that as the saidsuper-negative-energization of the control electrode is increased,thefamperage reaches a maximum value again, Aand at still higher degrecsof super-negative energization, vbegins to decrease again.

The above described control, over a range of higherand higher Vdegreesof negative energization `of the control electrode, including the twodescribed methods, .by which the amperage is caused to begin at a firstmaximum, to decrease toa minimum, and .again'to increase to a secondmaximum, Amay be considered here as a first phase ofthe control, .and .Ihave discovered that the control goes through other and successivegenerally similar phases of control; that is to say, as the negativeenergization increased higher and higher the amperage decreases from thesaid second maximum to asecond minimum, and then rises to a thirdmaximum; and then decreases from the third maximum to a third minimum`and then rises to a `fourth maximum; and that .there .are several .of.these successive phases of control,

.The characteristics of the above described changes of amperageoccurring upon increasing the negative energization of the controlelectrode are illustrated in Fig. 4 of the drawing; ordinate valuesrepresenting amperage, and abscissa values 'representingnegative'corrtrol electrode energization.

A more stable and otherwise satisfactory control of the amperage liowingthrough the tube may be effected if alternating Jvoltage be imr pressedupon the control electrode out of phase with that impressed upon theanode and cathode. To this end the control of the effective amperage bycorresponding energization of the control electrode may be effected byvarying the phase relationship between the electrode energization andthe potential impressed upon the anode and cathode but I prefer toeffect this control as referred to by utilizing a fixed angular phasedisplacement of the control electrode energization and by varying theamount of the potential on the control electrode at this phasedisplacement.

I have found that a suitable phase displacement is approximately 135degrees lag of the electrode potential behind the anode potentialalthough this exact displacement is not essential. This xed anglevariable potential electrode control is illustrated and described in myPatent No. 2,001,836, issued May 21, 1935, for a single range ofdischarge current values between a minimum and a maximum only in whichthe effective amperage varies inversely commensurably with the degree ofenergization of the control electrode.

In Fig. 2 is illustrated a representative circuit for effecting thistype of control with a tube such as has been described above. In thisiigure at I is shown the envelope, at Io the anode, at Ill the controlelectrode, at I2 the cathode, and at i, 8 and e the conductors leadingto the cathode. Supply mains I'I and I8 energize the primary I9 of atransformer the secondary Ztl of which supplies alternating current atsuitable voltage, such for example as five volts, to the above describedlament heating circuit. The supply mains also energize the primary 2! ofa transformer having a secondary 22 connected in a Aloop circuit with aresistor 23 and a condenser 24, the said loop circuit being alsoconnected to cathode I2 by a wire 25.

The control electrode Iii is connected as at 2S with the resistor 23 byan adjustable rheostat or potentiometer type of connection for adjustingthe potential on the control electrode, the .circuit for the electrodebeing considered from the wire 25, to the cathode I2, to the electrodeI4, to connection 26, through a part of the resistor 23, back to theWire 25. The condenser 24 may be adjusted to cause the potential on theelectrode Il! to be out of phase with the potential across the anode Illand cathode I2 as described, and at this xed phase displacement, whichas stated above is preferably but not necessarily of the order of 135degrees behind the anode cathode potential, the actual potential on thecontrol electrode Ill may be adjusted by the adjustable connection at25; and the polarity of this potential, predetermined by the transformer2 I--22, is negative with respect to the cathode when the anode ispositive with respect to the cathode, and is herein referred to asnegative with that meaning as mentioned hereinbefore.

As illustrative of suitable quantities for parts of the circuit of Fig.2, it may be added here that for a rectier as described above having acontinuous main current carrying capacity of 2% amperes, the capacity ofthe condenser 2t may suitably be .019 microfarad; and the resistance inthe resistor 23 may suitably be of the order.

of 150,000 ohms; and the voltage across the resistor provided by thetransformer secondary 22 may suitably be 600 volts, for supply mainsI'I, I8 at 110 volts 60 cycles. With the xed phase displacement referredto, the electrode connection at 26 may be adjusted to zero` electrodepotential, at which the full 21/2 amperes will flow in the main loadcircuit on each half wave, from the cathode to the anode of the tube;and if the negative potential on the control electrode I4 be adjusted toraise it above zero value, the tube will pass current later in each halfwave and the effective amperage in the load circuit will be decreased;and at approximately 450 volts on the electrode it the main current willbe practically cut off or reduced to a low minimum; and if the potentialon the electrode It be adjusted to raise it negatively to asuper-negative degree beyond 450 volts, current will again flow and theeffective amperagevvill be greater for higher electrode voltages; andvice versa, less for lesser electrode voltages in this super-negativerange. It will be noted that the quantities here given are suitable forthe above identied first phase of control, and it will be understood bythose skilled in the art how to adapt the quantities of the energizingcircuit to the higher potentials suitable for the succeeding phases ofcontrol.

As mentioned hereinbefore, rectier tubes of the gaseous discharge typeare known containing a gas such as argon in the envelope. In the abovedescribed tube, I also prefer to employ as stated a gas such as argonbut I have found that the pressure of the gas within the envelope shouldbe taken into account. For any pressure utilized the control electrodeenergization should correspond when control or variation of the currentflow by the electrode energization is Wanted. If a low gas pressure isused, the electrode voltage to normally cut off current ovv or reduce itto a minimum is lower and if the pressure is high, it is higher.

I have found that, taking into account the voltage drop and loss ofenergy through the tube and the optimum control conditions for varyingthe current by the electrode from zero or a minimum to the maximumdischarge current of the tube, a suitable pressure is of the order of to110 microns of mercury; and I therefore prefer to use that pressure ofargon in the tube for ordinary applications.

In alternating current installations in which variation of the flow ofcurrent through the tube is not wanted. and all that is wanted isinitiation and interruption of the current by electrode energization,the negative electrode may be energized at a phase displacement ofdegrees with respect to the anode cathode potential. Also while I havedescribed the control of variation of the current flow through the tubeby utilizing a control electrode energized negatively out of phase withthe anode cathode, and by adjusting the electrode potential by arheostat at a fixed I phase displacement. it is to be understood that myinvention may likewise be practiced by the known means of adjusting thephase displacement of the control electrode energization with respect tothe anode-cathode potential.

My invention will operate as described, using a tube constructed asdescribed in connection with Figs. 1 and 3 of the drawing` and asillustrated therein, and having the arrangement and proportion of thedescribed parts shown in these figures of the drawing; and whenenergized and controlled as described by a circuit such as that of Fig.2 of the drawing, having the quantitative circuit factors stated in theforegoing description.

My invention is not limited however in every respect to the exactdetails of construction illustrated and described. inasmuch as changesand modifications thereof may be made within the spirit of my inventionWithout sacrificing its 75" advantagesfandtwithin:thescope othefappendedf- Eorrexample'ltheftubeof my invention; may-besnsedcinmultiple back-to-back arrangement to..pass'fatfulhwavezof. alternatingcurrenti.

IrThe: method: oit controllingI the current` amperagesin' an`electricrzcircuit; which includes: connectingin; thea-circuit:the:anodeVand thermoemissivefcatlrodeofa; rectier" gaseous Ydischarge electronic:tulo'ef.A comprising at gas iilled envelopeinlwhichthe'anodeand-Icathode are spaced apart andacontrolxelectrodeinztne form-r of aloand surrounding:V the. envelopetinazone between the anoxi'tandtcathode'; impressing ontheanodeand catliodeffalternatingfpotental -fsuiicientA torcause' tleftubevtopass currentgenergizing the control electrodefwitli alternatingipotential atv thefrequency of-itli'e impressed-potential, and negative withrespeci'r'ltmthe*cathodewhen.the anode is positiveA` withz respecttto'the cathode; and causing currenti in the-ciicuitltoflirstrdecrease andtlienf: increasey by continuously increasing theenergizationoffth'e:control electrode from a value at'wiiichcurrent;ynou/sin` the circuit to a value atl Wlfiicitiscuti'o-'and on througharangeo valnestlieyondtlie'- cutoi value;

2.-' Tlie method54| of controlling the current' a-nlpera'ge".in3 an`electric` circuit; which includes: cunn'ectiiigy in xtliei circuitftlie anode and thermoernissi-'ve cathode*ofal rectifier Vgaseousdischarge electronic f tubef comprising-f' a gas4 nlled envelopeWnieli-tlieanodeandcathode are spaced apart andT acont'rol'electrode intheform of a band surrounding thief-envelope ina zonneV between theanode and cathode; impressing on the anod'eand catlf'i'oele` alternatingpotential Y sufficient to cause the tulo'ertopass-current; energizingthe control electrode Witli alternating potential at the fre- (fuencyoftheimpr-'essedi potential, and negative 35 Numberwithzrespectztofthezcathodel when the anode isf positiveWitlfrl respectito the' cathode; and causing. currentin the circuit to first decreaseand then increase byenergizing` the control electrode-ata 1valuezbeyond'the cutoi value to cause a high thetubeto pass current;energizing the control electrodewith alternating potential at thefrequencyof. the impressed potential, and negative Withv respect to thecathode when the anode isy positive with respect to the cathode; andcausing currentY in the circuit to rst increase and then decrease;y byenergizing the control electrode at a value beyondA the cut off Value tocause a lowvalue of'current to flow and continuously increasing thecontrol electrode energization.

PALMERH. CRAIG.

REFERENCES GITED The following references are of record in the le of'this patent:

UNITED STATES PATENTS Name Date Ile Van Nov. l5, 1932 Craig May 21, 1935Swart Dec. 28, 1937V

